3,869 research outputs found
A database system to support image algorithm evaluation
The design is given of an interactive image database system IMDB, which allows the user to create, retrieve, store, display, and manipulate images through the facility of a high-level, interactive image query (IQ) language. The query language IQ permits the user to define false color functions, pixel value transformations, overlay functions, zoom functions, and windows. The user manipulates the images through generic functions. The user can direct images to display devices for visual and qualitative analysis. Image histograms and pixel value distributions can also be computed to obtain a quantitative analysis of images
Observing Coherence Effects in an Overdamped Quantum System
It is usually considered that the spectrum of an optical cavity coupled to an
atomic medium does not exhibit a normal-mode splitting unless the system
satisfies the strong coupling condition, meaning the Rabi frequency of the
coherent coupling exceeds the decay rates of atom and cavity excitations. Here
we show that this need not be the case, but depends on the way in which the
coupled system is probed. Measurements of the reflection of a probe laser from
the input mirror of an overdamped cavity reveal an avoided crossing in the
spectrum which is not observed when driving the atoms directly and measuring
the Purcell-enhanced cavity emission. We understand these observations by
noting a formal correspondence with electromagnetically-induced transparency of
a three-level atom in free space, where our cavity acts as the absorbing medium
and the coupled atoms play the role of the control field
Short gamma-ray bursts within 200 Mpc
We present a systematic search for short-duration gamma-ray bursts (GRBs) in the local Universe based on 14 yr of observations with the Neil Gehrels Swift Observatory. We cross-correlate the GRB positions with the GLADE catalogue of nearby galaxies, and find no event at a distance ≲100 Mpc and four plausible candidates in the range 100 Mpc ≲ D ≲ 200 Mpc. Although affected by low statistics, this number is higher than the one expected for chance alignments to random galaxies, and possibly suggests a physical association between these bursts and nearby galaxies. By assuming a local origin, we use these events to constrain the range of properties for X-ray counterparts of neutron star mergers. Optical upper limits place tight constraints on the onset of a blue kilonova, and imply either low masses (≲10−3M⊙) of lanthanide-poor ejecta or unfavorable orientations (θ_(obs) ≳ 30 deg). Finally, we derive that the all-sky rate of detectable short GRBs within 200 Mpc is 1.3^(+1.7)_(−0.8) yr⁻¹ (68 per cent confidence interval), and discuss the implications for the GRB outflow structure. If these candidates are instead of cosmological origin, we set a upper limit of ≲2.0 yr⁻¹ (90 per cent confidence interval) to the rate of nearby events detectable with operating gamma-ray observatories, such as Swift and Fermi
Short gamma-ray bursts within 200 Mpc
We present a systematic search for short-duration gamma-ray bursts (GRBs) in the local Universe based on 14 yr of observations with the Neil Gehrels Swift Observatory. We cross-correlate the GRB positions with the GLADE catalogue of nearby galaxies, and find no event at a distance ≲100 Mpc and four plausible candidates in the range 100 Mpc ≲ D ≲ 200 Mpc. Although affected by low statistics, this number is higher than the one expected for chance alignments to random galaxies, and possibly suggests a physical association between these bursts and nearby galaxies. By assuming a local origin, we use these events to constrain the range of properties for X-ray counterparts of neutron star mergers. Optical upper limits place tight constraints on the onset of a blue kilonova, and imply either low masses (≲10−3M⊙) of lanthanide-poor ejecta or unfavorable orientations (θ_(obs) ≳ 30 deg). Finally, we derive that the all-sky rate of detectable short GRBs within 200 Mpc is 1.3^(+1.7)_(−0.8) yr⁻¹ (68 per cent confidence interval), and discuss the implications for the GRB outflow structure. If these candidates are instead of cosmological origin, we set a upper limit of ≲2.0 yr⁻¹ (90 per cent confidence interval) to the rate of nearby events detectable with operating gamma-ray observatories, such as Swift and Fermi
Platelet-Derived Growth Factor Receptor β Is Critical for Zebrafish Intersegmental Vessel Formation
Background: Platelet-derived growth factor receptor β (PDGFRβ) is a tyrosine kinase receptor known to affect vascular development. The zebrafish is an excellent model to study specific regulators of vascular development, yet the role of PDGF signaling has not been determined in early zebrafish embryos. Furthermore, vascular mural cells, in which PDGFRβ functions cell autonomously in other systems, have not been identified in zebrafish embryos younger than 72 hours post fertilization. Methodology/Principal Findings: In order to investigate the role of PDGFRβ in zebrafish vascular development, we cloned the highly conserved zebrafish homolog of PDGFRβ. We found that pdgfrβ is expressed in the hypochord, a developmental structure that is immediately dorsal to the dorsal aorta and potentially regulates blood vessel development in the zebrafish. Using a PDGFR tyrosine kinase inhibitor, a morpholino oligonucleotide specific to PDGFRβ, and a dominant negative PDGFRβ transgenic line, we found that PDGFRβ is necessary for angiogenesis of the intersegmental vessels. Significance/Conclusion: Our data provide the first evidence that PDGFRβ signaling is required for zebrafish angiogenesis. We propose a novel mechanism for zebrafish PDGFRβ signaling that regulates vascular angiogenesis in the absence of mural cells
Evidence of extended emission in GRB 181123B and other high-redshift short GRBs
We study the high-energy properties of GRB 181123B, a short gamma-ray burst
(sGRB) at redshift z1.75. We show that, despite its nominal short
duration with T90 < 2 s, this burst display evidence of a temporally extended
emission (EE) at high energies and that the same trend is observed in the
majority of sGRBs at z > 1. We discuss the impact of instrumental selection
effects on the GRB classification, stressing that the measured T90 is not an
unambiguous indicator of the burst physical origin. By examining their
environment (e.g. stellar mass, star formation, offset distribution), we find
that these high-z sGRBs share many properties of long GRBs at a similar
distance and are consistent with a short-lived progenitor system. If produced
by compact binary mergers, these sGRBs with EE may herald a larger population
of sGRBs in the early universe.Comment: 10 pages, 6 figures, 2 tables. Submitted to ApJ
Race/Ethnicity, Color-Blind Racial Attitudes, and Multicultural Counseling Competence: The Moderating Effects of Multicultural Counseling Training
Increasing trainees' multicultural counseling competence (MCC) has been a hot topic in counseling. Scholars have identified predictors (e.g., race/ethnicity, color-blindness) of MCC, and educators provide multicultural training for trainees. Using a sample of 370 psychology trainees, this study examined whether multicultural training (a) moderated racial/ethnic differences on MCC and (b) changed the relationship between color-blindness and MCC. Results indicated a significant interaction effect of race/ethnicity (i.e., White vs. ethnic minority) and multicultural training on multicultural awareness, but not on multicultural knowledge. Specifically, at lower levels of training, racial/ethnic minority trainees had significantly higher multicultural awareness than their White counterparts; at higher levels of training, no significant difference was found. Described differently, more training significantly enhanced Whites' multicultural awareness, but did not enhance racial/ethnic minority trainees' awareness. Additionally, there was a significant interaction effect of color-blindness and multicultural training on multicultural knowledge, but not on multicultural awareness. The association between color-blindness and multicultural knowledge was stronger at higher levels of multicultural training than at lower levels of training. Alternatively, the effect of training on enhancing knowledge was stronger for those with lower color-blindness than for those with higher color-blindness
The afterglow and kilonova of the short GRB 160821B
GRB 160821B is a short duration gamma-ray burst (GRB) detected and localized
by the Neil Gehrels Swift Observatory in the outskirts of a spiral galaxy at
z=0.1613, at a projected physical offset of 16 kpc from the galaxy's center. We
present X-ray, optical/nIR and radio observations of its counterpart and model
them with two distinct components of emission: a standard afterglow, arising
from the interaction of the relativistic jet with the surrounding medium, and a
kilonova, powered by the radioactive decay of the sub-relativistic ejecta.
Broadband modeling of the afterglow data reveals a weak reverse shock
propagating backward into the jet, and a likely jet-break at 3.5 d. This is
consistent with a structured jet seen slightly off-axis while expanding into a
low-density medium. Analysis of the kilonova properties suggests a rapid
evolution toward red colors, similar to AT2017gfo, and a low nIR luminosity,
possibly due to the presence of a long-lived neutron star. The global
properties of the environment, the inferred low mass (M_ej < 0.006 Msun) and
velocities (v > 0.05 c) of lanthanide-rich ejecta are consistent with a binary
neutron star merger progenitor.Comment: 14 pages, 6 figures, MNRAS, in press. Moderate revision, added Figure
5 and X-ray data to Table
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